Include a Preferences option to choose one of the following kinds of frames that will automatically be added around each screenshot:
• A one-pixel black hairline
• A drop shadow
There are other options that would be nice (fade to black, fade to white), but at the very least, the ability to add the black hairline is a must-have option. My previous screenshot app (SnapzProX, now extinct) offered many options that are not available in Monosnap, and other current screenshot apps.
I used SnapzProX for 20 years, but it died with macOS Mojave. I would PAY for a screenshot app that included all the features SnapzProX provided for still screenshots.
(See attached Snapz Pro X 2.1 Manual (trimmed).pdf, which I’ve trimmed to fit the 2.5MB filesize allowed for attachments. Most of the excluded content pertains to video capture, which isn’t as important to me as the static image capture features.)